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A094741 Number of primes of the form k+1 where k is coprime to n, k < n. 1

%I

%S 0,1,2,1,3,1,4,1,3,1,5,1,6,1,3,1,7,1,8,1,5,1,9,1,8,1,6,1,10,1,11,1,6,

%T 1,8,1,12,1,7,1,13,1,14,1,6,1,15,1,13,1,9,1,16,1,12,1,10,1,17,1,18,1,

%U 10,1,13,1,19,1,10,1,20,1,21,1,9,1,16,1,22,1,12,1,23,1,18,1,12

%N Number of primes of the form k+1 where k is coprime to n, k < n.

%C If n is a prime, a(n) = pi(n). If n is even, a(n) = 1.

%t A094741[ n_ ] := Length[ Select[ Select[ Range[ n - 1 ], GCD[ #, n ] == 1 & ] + 1, PrimeQ ] ]; Table[ A094741[ i ], {i, 1, 100} ] (* Keith Schneider, Jul 03 2007 *)

%K nonn

%O 1,3

%A _Amarnath Murthy_, May 24 2004

%E More terms from Keith Schneider, Jul 03 2007

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Last modified January 26 18:20 EST 2022. Contains 350599 sequences. (Running on oeis4.)